Revert "Zone support for Futures."

sdk/lib/async/zone.dart

-// Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
-// for details. All rights reserved. Use of this source code is governed by a
-// BSD-style license that can be found in the LICENSE file.
-
-part of dart.async;
-
-/**
- * A Zone represents the asynchronous version of a dynamic extent. Asynchronous
- * callbacks are executed in the zone they have been queued in. For example,
- * the callback of a `future.then` is executed in the same zone as the one where
- * the `then` was invoked.
- */
-abstract class _Zone {
-  /// The currently running zone.
-  static _Zone _current = new _DefaultZone();
-
-  static _Zone get current => _current;
-
-  void handleUncaughtError(error);
-
-  /**
-   * Returns true if `this` and [otherZone] are in the same error zone.
-   */
-  bool inSameErrorZone(_Zone otherZone);
-
-  /**
-   * Returns a zone for reentry in the zone.
-   *
-   * The returned zone is equivalent to `this` (and frequently is indeed
-   * `this`).
-   *
-   * The main purpose of this method is to allow `this` to attach debugging
-   * information to the returned zone.
-   */
-  _Zone fork();
-
-  /**
-   * Tells the zone that it needs to wait for one more callback before it is
-   * done.
-   *
-   * Use [executeCallback] or [cancelCallbackExpectation] when the callback is executed
-   * (or canceled).
-   */
-  void expectCallback();
-
-  /**
-   * Tells the zone not to wait for a callback anymore.
-   *
-   * Prefer calling [executeCallback], instead. This method is mostly useful
-   * for repeated callbacks (for example with [Timer.periodic]). In this case
-   * one should should call [expectCallback] when the repeated callback is
-   * initiated, and [cancelCallbackExpectation] when the [Timer] is canceled.
-   */
-  void cancelCallbackExpectation();
-
-  /**
-   * Executes the given callback in this zone.
-   *
-   * Decrements the number of callbacks this zone is waiting for (see
-   * [expectCallback]).
-   */
-  void executeCallback(void fun());
-
-  /**
-   * Same as [executeCallback] but catches uncaught errors and gives them to
-   * [handleUncaughtError].
-   */
-  void executeCallbackGuarded(void fun());
-
-  /**
-   * Same as [executeCallback] but does not decrement the number of
-   * callbacks this zone is waiting for (see [expectCallback]).
-   */
-  void executePeriodicCallback(void fun());
-
-  /**
-   * Same as [executePeriodicCallback] but catches uncaught errors and gives
-   * them to [handleUncaughtError].
-   */
-  void executePeriodicCallbackGuarded(void fun());
-
-  /**
-   * Runs [fun] asynchronously in this zone.
-   */
-  void runAsync(void fun());
-
-  /**
-   * Creates a Timer where the callback is executed in this zone.
-   */
-  Timer createTimer(Duration duration, void callback());
-
-  /**
-   * Creates a periodic Timer where the callback is executed in this zone.
-   */
-  Timer createPeriodicTimer(Duration duration, void callback(Timer timer));
-
-  /**
-   * The error zone is the one that is responsible for dealing with uncaught
-   * errors. Errors are not allowed to cross zones with different error-zones.
-   */
-  _Zone get _errorZone;
-
-  /**
-   * Adds [child] as a child of `this`.
-   *
-   * This usually means that the [child] is in the asynchronous dynamic extent
-   * of `this`.
-   */
-  void _addChild(_Zone child);
-
-  /**
-   * Removes [child] from `this`' children.
-   *
-   * This usually means that the [child] has finished executing and is done.
-   */
-  void _removeChild(_Zone child);
-}
-
-/**
- * Basic implementation of a [_Zone]. This class is intended for subclassing.
- */
-class _ZoneBase implements _Zone {
-  /// The parent zone. [null] if `this` is the default zone.
-  final _Zone _parentZone;
-
-  /// The children of this zone. A child's [_parentZone] is `this`.
-  // TODO(floitsch): this should be a double-linked list.
-  final List<_Zone> _children = <_Zone>[];
-
-  /// The number of outstanding (asynchronous) callbacks. As long as the
-  /// number is greater than 0 it means that the zone is not done yet.
-  int _openCallbacks = 0;
-
-  bool _isExecutingCallback = false;
-
-  _ZoneBase(this._parentZone) {
-    _parentZone._addChild(this);
-  }
-
-  _ZoneBase._defaultZone() : _parentZone = null {
-    assert(this is _DefaultZone);
-  }
-
-  _Zone get _errorZone => _parentZone._errorZone;
-
-  void handleUncaughtError(error) {
-    _parentZone.handleUncaughtError(error);
-  }
-
-  bool inSameErrorZone(_Zone otherZone) => _errorZone == otherZone._errorZone;
-
-  _Zone fork() => this;
-
-  expectCallback() => _openCallbacks++;
-
-  cancelCallbackExpectation() {
-    _openCallbacks--;
-    _checkIfDone();
-  }
-
-  /**
-   * Cleans up this zone when it is done.
-   *
-   * This releases internal memore structures that are no longer necessary.
-   *
-   * A zone is done when its dynamic extent has finished executing and
-   * there are no outstanding asynchronous callbacks.
-   */
-  _dispose() {
-    if (_parentZone != null) {
-      _parentZone._removeChild(this);
-    }
-  }
-
-  /**
-   * Checks if the zone is done and doesn't have any outstanding callbacks
-   * anymore.
-   *
-   * This method is called when an operation has decremented the
-   * outstanding-callback count, or when a child has been removed.
-   */
-  void _checkIfDone() {
-    if (!_isExecutingCallback && _openCallbacks == 0 && _children.isEmpty) {
-      _dispose();
-    }
-  }
-
-  /**
-   * Executes the given callback in this zone.
-   *
-   * Decrements the open-callback counter and checks (after the call) if the
-   * zone is done.
-   */
-  void executeCallback(void fun()) {
-    _openCallbacks--;
-    this._runUnguarded(fun);
-  }
-
-  /**
-   * Same as [executeCallback] but catches uncaught errors and gives them to
-   * [handleUncaughtError].
-   */
-  void executeCallbackGuarded(void fun()) {
-    _openCallbacks--;
-    this._runGuarded(fun);
-  }
-
-  /**
-   * Same as [executeCallback] but doesn't decrement the open-callback counter.
-   */
-  void executePeriodicCallback(void fun()) {
-    this._runUnguarded(fun);
-  }
-
-  /**
-   * Same as [executePeriodicCallback] but catches uncaught errors and gives
-   * them to [handleUncaughtError].
-   */
-  void executePeriodicCallbackGuarded(void fun()) {
-    this._runGuarded(fun);
-  }
-
-  _runInZone(fun(), bool handleUncaught) {
-    if (identical(_Zone._current, this)
-        && !handleUncaught
-        && _isExecutingCallback) {
-      // No need to go through a try/catch.
-      return fun();
-    }
-
-    _Zone oldZone = _Zone._current;
-    _Zone._current = this;
-    // While we are executing the function we don't want to have other
-    // synchronous calls to think that they closed the zone. By incrementing
-    // the _openCallbacks count we make sure that their test will fail.
-    // As a side effect it will make nested calls faster since they are
-    // (probably) in the same zone and have an _openCallbacks > 0.
-    bool oldIsExecuting = _isExecutingCallback;
-    _isExecutingCallback = true;
-    // TODO(430): remove second try when VM bug is fixed.
-    try {
-      try {
-        return fun();
-      } catch(e, s) {
-        if (handleUncaught) {
-          handleUncaughtError(_asyncError(e, s));
-        } else {
-          rethrow;
-        }
-      }
-    } finally {
-      _isExecutingCallback = oldIsExecuting;
-      _Zone._current = oldZone;
-      _checkIfDone();
-    }
-  }
-
-  /**
-   * Runs the function and catches uncaught errors.
-   *
-   * Uncaught errors are given to [handleUncaughtError].
-   */
-  _runGuarded(void fun()) {
-    return _runInZone(fun, true);
-  }
-
-  /**
-   * Runs the function but doesn't catch uncaught errors.
-   */
-  _runUnguarded(void fun()) {
-    return _runInZone(fun, false);
-  }
-
-  runAsync(void fun()) {
-    _openCallbacks++;
-    _scheduleAsyncCallback(() {
-      _openCallbacks--;
-      _runGuarded(fun);
-    });
-  }
-
-  Timer createTimer(Duration duration, void callback()) {
-    return new _ZoneTimer(this, duration, callback);
-  }
-
-  Timer createPeriodicTimer(Duration duration, void callback(Timer timer)) {
-    return new _PeriodicZoneTimer(this, duration, callback);
-  }
-
-  void _addChild(_Zone child) {
-    _children.add(child);
-  }
-
-  void _removeChild(_Zone child) {
-    assert(!_children.isEmpty);
-    // Children are usually added and removed fifo or filo.
-    if (identical(_children.last, child)) {
-      _children.length--;
-      _checkIfDone();
-      return;
-    }
-    for (int i = 0; i < _children.length; i++) {
-      if (identical(_children[i], child)) {
-        _children[i] = _children[_children.length - 1];
-        _children.length--;
-        // No need to check for done, as otherwise _children.last above would
-        // have triggered.
-        assert(!_children.isEmpty);
-        return;
-      }
-    }
-    throw new ArgumentError(child);
-  }
-}
-
-/**
- * The default-zone that conceptually surrounds the `main` function.
- */
-class _DefaultZone extends _ZoneBase {
-  _DefaultZone() : super._defaultZone();
-
-  _Zone get _errorZone => this;
-
-  handleUncaughtError(error) {
-    _scheduleAsyncCallback(() {
-      print("Uncaught Error: ${error}");
-      var trace = getAttachedStackTrace(error);
-      _attachStackTrace(error, null);
-      if (trace != null) {
-        print("Stack Trace:\n$trace\n");
-      }
-      throw error;
-    });
-  }
-}
-
-typedef void _CompletionCallback();
-
-/**
- * A zone that executes a callback when the zone is dead.
- */
-class _WaitForCompletionZone extends _ZoneBase {
-  final _CompletionCallback _onDone;
-
-  _WaitForCompletionZone(_Zone parentZone, this._onDone) : super(parentZone);
-
-  /**
-   * Runs the given function asynchronously. Executes the [_onDone] callback
-   * when the zone is done.
-   */
-  runWaitForCompletion(void fun()) {
-    return this._runUnguarded(fun);
-  }
-
-  _dispose() {
-    super._dispose();
-    _onDone();
-  }
-
-  String toString() => "WaitForCompletion ${super.toString()}";
-}
-
-typedef void _HandleErrorCallback(error);
-
-/**
- * A zone that collects all uncaught errors and provides them in a stream.
- * The stream is closed when the zone is done.
- */
-class _CatchErrorsZone extends _WaitForCompletionZone {
-  final _HandleErrorCallback _handleError;
-
-  _CatchErrorsZone(_Zone parentZone, this._handleError, void onDone())
-    : super(parentZone, onDone);
-
-  _Zone get _errorZone => this;
-
-  handleUncaughtError(error) {
-    try {
-      _handleError(error);
-    } catch(e, s) {
-      if (identical(e, s)) {
-        _parentZone.handleUncaughtError(error);
-      } else {
-        _parentZone.handleUncaughtError(_asyncError(e, s));
-      }
-    }
-  }
-
-  /**
-   * Runs the given function asynchronously. Executes the [_onDone] callback
-   * when the zone is done.
-   */
-  runWaitForCompletion(void fun()) {
-    return this._runGuarded(fun);
-  }
-
-  String toString() => "WithErrors ${super.toString()}";
-}
-
-typedef void _TimerCallback();
-
-/**
- * A [Timer] class that takes zones into account.
- */
-class _ZoneTimer implements Timer {
-  final _Zone _zone;
-  final _TimerCallback _callback;
-  Timer _timer;
-  bool _isDone = false;
-
-  _ZoneTimer(this._zone, Duration duration, this._callback) {
-    _zone.expectCallback();
-    _timer = _createTimer(duration, this.run);
-  }
-
-  void run() {
-    _isDone = true;
-    _zone.executeCallbackGuarded(_callback);
-  }
-
-  void cancel() {
-    if (!_isDone) _zone.cancelCallbackExpectation();
-    _isDone = true;
-    _timer.cancel();
-  }
-}
-
-typedef void _PeriodicTimerCallback(Timer timer);
-
-/**
- * A [Timer] class for periodic callbacks that takes zones into account.
- */
-class _PeriodicZoneTimer implements Timer {
-  final _Zone _zone;
-  final _PeriodicTimerCallback _callback;
-  Timer _timer;
-  bool _isDone = false;
-
-  _PeriodicZoneTimer(this._zone, Duration duration, this._callback) {
-    _zone.expectCallback();
-    _timer = _createPeriodicTimer(duration, this.run);
-  }
-
-  void run(Timer timer) {
-    assert(identical(_timer, timer));
-    _zone.executePeriodicCallbackGuarded(() { _callback(this); });
-  }
-
-  void cancel() {
-    if (!_isDone) _zone.cancelCallbackExpectation();
-    _isDone = true;
-    _timer.cancel();
-  }
-}
-
-/**
- * Runs [body] in its own zone.
- *
- * If [onError] is non-null the zone is considered an error zone. All uncaught
- * errors, synchronous or asynchronous, in the zone are caught and handled
- * by the callback.
- *
- * [onDone] (if non-null) is invoked when the zone has no more outstanding
- * callbacks.
- *
- * Examples:
- *
- *     runZonedExperimental(() {
- *       new Future(() { throw "asynchronous error"; });
- *     }, onError: print);  // Will print "asynchronous error".
- *
- * The following example prints "1", "2", "3", "4" in this order.
- *
- *     runZonedExperimental(() {
- *       print(1);
- *       new Future.value(3).then(print);
- *     }, onDone: () { print(4); });
- *     print(2);
- *
- * Errors may never cross error-zone boundaries. This is intuitive for leaving
- * a zone, but it also applies for errors that would enter an error-zone.
- * Errors that try to cross error-zone boundaries are considered uncaught.
- *
- *     var future = new Future.value(499);
- *     runZonedExperimental(() {
- *       future = future.then((_) { throw "error in first error-zone"; });
- *       runZonedExperimental(() {
- *         future = future.catchError((e) { print("Never reached!"); });
- *       }, onError: (e) { print("unused error handler"); });
- *     }, onError: (e) { print("catches error of first error-zone."); });
- *
- */
-runZonedExperimental(body(), { void onError(error), void onDone() }) {
-  // TODO(floitsch): we probably still want to install a new Zone.
-  if (onError == null && onDone == null) return body();
-  if (onError == null) {
-    _WaitForCompletionZone zone =
-        new _WaitForCompletionZone(_Zone._current, onDone);
-    return zone.runWaitForCompletion(body);
-  }
-  if (onDone == null) onDone = _nullDoneHandler;
-  _CatchErrorsZone zone = new _CatchErrorsZone(_Zone._current, onError, onDone);
-  return zone.runWaitForCompletion(body);
-}